a) Field of the Invention
The invention relates to a device for achieving different tilt angles of planar objects relative to a reference plane and rotation of the object about an axis aligned perpendicular to the surface of the object. Devices of this kind can be used to position flat objects and, in particular, for purposes of inspecting substrates, such as semiconductor wafers or flat panels.
b) Description of the Related Art
Technical solutions known hitherto operated on the basis of a three-dimensionally adjustable receiving element for the semiconductor wafers to be inspected, said element being provided with a vacuum suction device serving to hold the wafer. The receiving element holds the semiconductor wafer during the inspection process and, by virtue of its construction, allows rotary motion at different angles of tilt relative to the illumination beam path or direction of inspection.
In a known positioning system of this kind as disclosed, for example, in U.S. Pat. No. 5,096,291, use is made of a holder which is mounted in an articulated manner to allow it to perform the movements. Actuating elements in the form of tappets transmit the movements to the holder from a ring, the angle of tilt of which can be adjusted and which is coupled concentrically to a rotatable spindle.
All solutions which operate with the aid of a vacuum suction device have the disadvantage that viewing from the rear is severely limited.
When the semiconductor wafer is held by largely surface-type contact as hitherto, migration can have an unwanted disruptive effect on the intended wafer properties. Moreover, more recent technological requirements mean that the semiconductor wafer must only be brought into contact with holding elements in a narrowly defined edge region. The entire rear area is also unsuitable as a contact area.
The system known from U.S. Pat. No. 5,096,291 also entails a further restriction due to the use of tappets, which allow only a limited range of motion to be achieved by the holder.